1. Technical Field of the Invention
The present invention pertains in general to a method and apparatus for storing mobile station location information in a mobile radio network and, more particularly, but not by way of limitation, to a method and apparatus for caching location information of transmitting mobile stations in a gateway packet switch node.
2. Description of the Related Art
In a mobile radio network, a geographical service area is divided into a plurality of cells. Communication services are provided to mobile stations moving between the cells by a plurality of base stations. The base stations are grouped together in a plurality of Mobile Services Switching Centers (MSCs) which effectuates communication between the individual base stations and the mobile radio network. Communication with other networks outside of the mobile radio network is effectuated via a Gateway Mobile Services Switching Center (GMSC). In a mobile radio network which provides packet data services, the Mobile Services Switching Centers are referred to as Visiting Packet Switch Nodes (Visiting PSNs) and the Gateway Mobile Services Switching Center is referred to as a Gateway Packet Switch Node (Gateway PSN).
When a mobile station in a mobile radio network receives a voice call, whether it be from a party outside the mobile radio network or from a subscriber to the mobile radio network, the call is routed to the GMSC. The GMSC xe2x80x9clooks upxe2x80x9d location information for that called party contained in a Home Location Register (HLR) to determine the current location of the mobile station. The HLR stores the current location information of the mobile station. The location information is updated by the Visiting PSN every time the mobile station performs a registration with the Visiting PSN. Using this information, the GMSC routes the call to the appropriate servicing MSC which further routes the call to the base station currently serving the mobile station thereby establishing a call between the party calling the mobile station and the mobile station being called.
Packet data services are being introduced at an increasing rate into mobile radio networks. Packet data services provide an efficient connection between digital terminal equipment connected to mobile stations in a mobile radio network and other digital terminal equipment both internal and external to the mobile radio network. Using a packet data service, data is transmitted as discrete data packets. When a data packet is transmitted from digital terminal equipment connected to a mobile station, each packet sent by the digital terminal equipment includes the address of the destination digital terminal equipment. Likewise, when the Gateway PSN receives incoming data packets for the digital terminal equipment connected to the mobile station, the logical address of the mobile station is included with each received data packet.
Establishing the voice call requires that the GMSC access the HLR once to determine the location of the mobile station being called; however, in a mobile radio network which provides packet data services, the number of accesses which the Gateway PSN makes to the HLR is greatly increased. In order for the Gateway PSN to route the data packet to the mobile station, the Gateway PSN accesses the HLR to determine the physical location of the mobile station. Because every data packet sent to the mobile station is sent autonomously, the Gateway PSN must access the HLR to determine location information for each data packet which greatly increases the communication between the Gateway PSN and the HLR as compared to voice calls.
To reduce the number of accesses which the Gateway PSN makes to the HLR, it has been proposed to cache the location information contained within the HLR in a cache located within the Gateway PSN. Although this approach reduces the number of accesses the Gateway PSN makes to the HLR it has certain drawbacks. The proposed cache needs to be large enough to hold the location of all the mobile stations operating within the mobile radio network. Otherwise, when a first packet for a mobile station, not included in the cache, is received by the Gateway PSN, the Gateway PSN must access the HLR to retrieve location information for the mobile station. Furthermore, whenever a mobile station moves between base stations the location information is updated in the HLR thereby requiring the cache to be updated. Maintaining the cache thus becomes overhead for the Gateway PSN.
It would be advantageous to devise a method and apparatus to cache mobile station location information in a Gateway PSN which reduces the number of accesses the Gateway PSN needs to make to the HLR. It would further be advantageous if such a method and apparatus did not store the location of all the mobile stations operating within the mobile radio network but instead, anticipated the mobile station location information which is most likely to be needed.
The present invention comprises a method and apparatus for caching mobile station location information including a gateway packet switch node for receiving and transmitting data packets between a plurality of visiting packet switch nodes within a mobile radio network and at least one communication network and a cache memory located within the gateway packet switch for caching location information received with a data packet from a transmitting mobile station.
A communication packet, containing information pertaining to the location of a transmitting mobile station is received by the gateway packet switch node. The location information is extracted from the received communication packet and stored in a cache.
When a data packet addressed to a mobile station is received by the gateway packet switch node, a determination is made as to whether the location information pertaining to the mobile station is stored within the cache. If the location information is stored within the cache the location information is retrieved from the cache and the data packet is routed to the mobile station. Otherwise, the location information is retrieved from a home location register and the data packet is routed to the mobile station.